Axle assembly for low floor vehicle

ABSTRACT

An electric axle assembly includes a suspension frame and drive assemblies coupled to opposing sides of the suspension frame. The electric axle assembly engages with wheels of a vehicle for rotating the wheels to move the vehicle along a ground surface. A drive unit transfers motive force to the wheels through one or more gearsets and axle shafts.

CROSS-REFERENCE TO RELATED U.S. PATENT APPLICATION

This application claims the benefit of priority to U.S. ProvisionalApplication No. 62/812,039, filed Feb. 28, 2019, the disclosure of whichis incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to axle assemblies forvehicles, and more particularly, to an electric axle assembly for avehicle.

BACKGROUND

In order to aid ingress and egress, it is desirable for a motor vehicleto have a floor that is as low to the ground as possible. Busses andpeople carriers, commonly called low floor vehicles, are examples ofvehicles that benefit from a low floor height. By minimizing the floorheight, a step at a door of the vehicle may be eliminated, which in turnallows easier ingress and egress for vehicle passengers. Elimination ofsteps is especially beneficial to disabled passengers, and passengerscarrying items, such as strollers. Increasingly, manufacturers haveturned to electric and hybrid propulsion systems for low floor vehiclesfor increased performance and efficiency. In order to have the floor ofthe vehicle as low as possible, the drivetrain components are relocatedso as to reduce intrusions into the vehicle floor.

SUMMARY

According to an aspect of the present disclosure, an electric axleassembly may include a suspension frame, a first drive assembly and asecond drive assembly coupled to opposing sides of the suspension frame,a drive unit, and a drive train. A first wheel hub may be coupled to thefirst drive assembly and a second wheel hub may be coupled to the seconddrive assembly. The first and second wheel hubs may be arranged tosupport wheels for rotation about a first axis.

In illustrative embodiments, the drivetrain may include a first gearsetarranged in the first drive assembly, a second gearset arranged in thesecond drive assembly, and a portal axle extending between the first andsecond gearsets. The first gearset may be coupled to the first wheel huband the second gearset may be coupled to the second wheel hub. Theportal shaft may be arranged for rotation about a second axis offsetfrom the first axis.

In illustrative embodiments, the drive unit may be arranged in the firstdrive assembly and may be configured to provide motive force to adifferential of the first gearset. The portal shaft may be coupled tothe differential. The differential may be configured to transfer motiveforce to the first wheel hub through the first gearset and to the secondwheel hub through the portal shaft and second gearset.

In illustrative embodiments, the first gearset may include thedifferential, a stub shaft coupled to the differential, a first outputgearset coupled to the stub shaft, and a first planetary gearset coupledto the first output gearset and the first wheel hub. The differentialmay be arranged along the second axis. The second gearset may include asecond output gearset coupled to the portal shaft opposite of thedifferential and a second planetary gearset coupled to the second outputgearset and the second wheel hub.

In illustrative embodiments, a bridge of the suspension frame may beoffset from the first axis, and the portal shaft may be arranged tosubstantially align the bridge.

In illustrative embodiments, the differential may include a case, aspider gear coupled to the case for rotation with the case about thesecond axis, and side gears coupled to the portal shaft and stub shaft,respectively, and engaged with the spider gear.

In illustrative embodiments, the differential may include a case, a pairof planet gears coupled to the case for rotation with the case about thesecond axis, and side gears coupled to the portal shaft and stub shaft,respectively. The planet gears may be engaged with each other and withrespective ones of the side gears.

In illustrative embodiments, the first output gearset may include apinion gear coupled to the stub shaft and an output gear coupled to thefirst planetary gearset and engaged with the pinion gear.

In illustrative embodiments, the output gear may be arranged forrotation about the first axis.

In illustrative embodiments, the first planetary gearset may include asun gear coupled to the output gear for rotation about the first axis, aplanet gear arranged radially outward of the sun gear and engaged withthe sun gear, a ring gear arranged radially outward of the planet gearand engaged with the planet gear, and a carrier coupled to the planetgear and the first wheel hub. The ring gear may be stationary relativeto the first axis.

In illustrative embodiments, the second output gearset may include apinion gear coupled to the portal shaft and an output gear coupled tothe second planetary gearset and engaged with the pinion gear.

In illustrative embodiments, the output gear may be arranged forrotation about the first axis.

In illustrative embodiments, the second planetary gearset may include asun gear coupled to the output gear for rotation about the first axis, aplanet gear arranged radially outward of the sun gear and engaged withthe sun gear, a ring gear arranged radially outward of the planet gearand engaged with the planet gear, and a carrier coupled to the planetgear and the second wheel hub. The ring gear may be stationary relativeto the first axis.

In illustrative embodiments, the electric axle assembly may furtherinclude a drive gear coupled to the differential and arranged to receivemotive force from the drive unit.

In illustrative embodiments, the electric axle assembly may furtherinclude a transmission. The transmission may include a first input gearand second input gear coupled to a drive gear, a first output gear and asecond output gear rotatably mounted on a support shaft coupled to thedifferential, and a gear selector mounted on the support shaft. Thedrive gear may be arranged to receive motive force from the drive unit.The first input gear may be engaged with the first output gear and thesecond input gear may be engaged with the second output gear. The gearselector may be movable along the support shaft and rotatably fixedrelative to the support shaft. The gear selector may be configured toselectively engage with the first or second output gear to blockrotation of the engaged first or second output gear relative to thesupport shaft.

In illustrative embodiments, in a first configuration, the gear selectormay engage with the first output gear to block rotation of the firstoutput gear relative to the support shaft and allow rotation of thesecond output gear relative to the support shaft to provide a low ratioof the transmission. In a second configuration, the gear selector mayengage with the second output gear to block rotation of the secondoutput gear relative to the support shaft and allow rotation of thefirst output gear relative to the support shaft to provide a high ratioof the transmission.

In illustrative embodiments, the electric axle assembly may furtherinclude an actuator configured to move the gear selector to the firstand second configurations.

BRIEF DESCRIPTION OF THE DRAWINGS

The systems and methods described herein are illustrated by way ofexample and not by way of limitation in the accompanying figures(abbreviated as “Fig.” or “Figs.” herein). For simplicity and clarity ofillustration, elements illustrated in the figures are not necessarilydrawn to scale. For example, the dimensions of some elements may beexaggerated relative to other elements for clarity. Further, whereconsidered appropriate, reference labels have been repeated among thefigures to indicate corresponding or analogous elements.

FIG. 1 is a perspective view of an electric axle assembly for a lowfloor vehicle according to embodiments of the present disclosure.

FIG. 2 is a front elevation view of the electric axle assembly shown inFIG. 1.

FIG. 3 is a diagrammatic view of the electric axle assembly of FIG. 1.

FIG. 4 is a diagrammatic view of a differential of the electric axleassembly of FIG. 3.

FIG. 5 is a diagrammatic view of a planetary gearset of the electricaxle assembly of FIG. 3.

FIG. 6 is a diagrammatic view of another electric axle assembly for alow floor vehicle according to embodiments of the present disclosure.

FIG. 7 is a diagrammatic view of a differential of the electric axleassembly of FIG. 6.

FIG. 8 is a diagrammatic view of another electric axle assembly for alow floor vehicle according to embodiments of the present disclosure.

FIG. 9 is a view similar to FIG. 8 showing a bridge of a suspension fromof the electric axle assembly having a shortened width.

DETAILED DESCRIPTION

While the concepts of the present disclosure are susceptible to variousmodifications and alternative forms, specific exemplary embodimentsthereof have been shown by way of example in the drawings and willherein be described in detail. It should be understood, however, thatthere is no intent to limit the concepts of the present disclosure tothe particular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the disclosure as defined by the appendedclaims.

References in the specification to “one embodiment”, “an embodiment”,“an example embodiment”, etc., indicate that the embodiment describedmay include a particular feature, structure, or characteristic, butevery embodiment may not necessarily include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to effect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

An illustrative electric axle assembly 10 in accordance with the presentdisclosure is shown in FIGS. 1-3. The electric axle assembly 10 can beused, for example, in a low floor vehicle, such as a bus, to support thevehicle for travel over the ground and propel the vehicle. The electricaxle assembly 10 includes a suspension frame 12 and first and seconddrive assemblies 14, 16 coupled to opposing sides of the suspensionframe 12. The suspension frame 12 includes mounts 15 and a bridge 17.The suspension frame 12 attaches to a vehicle frame (not shown) throughthe mounts 15 and control arms 19 for supporting the drive assemblies14, 16 relative to the vehicle frame. In the illustrative embodiment,the mounts 15 are coupled to the drive assemblies 14, 16, and the driveassemblies 14, 16 are coupled to the bridge 17 to support the driveassemblies 14, 16 spaced apart from one another. In some embodiments,the mounts 15 are coupled to the drive assemblies 14, 16, and the bridge17 (comprising a pair of rails arranged along opposite sides of thedrive assemblies 14, 16) are coupled to the mounts 15 to support thedrive assemblies 14, 16 spaced apart from one another.

A drive unit 18, such as an electric motor, of the drive assembly 14provides motive force to a drivetrain 20 for rotating wheels 100 (shownin phantom in FIG. 2) mounted on wheel hubs 11, 13 about an axis A topropel the vehicle along the ground as shown in FIGS. 1 and 2. The wheelhubs 11, 13 allow attachment of the wheels 100 to the drive assemblies14, 16 for rotation with rotation of the drivetrain 20. The drivetrain20 includes a first gearset 22 of the first drive assembly 14, a secondgearset 24 of the second drive assembly 16, and a portal shaft 26coupled between the first and second gearsets 22, 24. The portal shaft26 is arranged for rotation about an axis B. The bridge 17 and portalshaft 26 are offset from the rotation axis A of the wheels 100 in orderto decrease the height of the low floor of the vehicle as shown in FIG.2. It is desirable for a height of the low floor of the vehicle to be aslow as possible and a width to be as wide as possible in order tomaximize capacity of the vehicle. In the illustrative embodiment, therotation axis B of the portal shaft 26 is offset from the rotation axisA of the wheels 100 and hubs 11, 13 by a distance D along a verticalaxis V. The bridge 17 is also positioned as low as possible, and theportal shaft 26 and bridge 17 can be aligned along a horizontal plane asshown in FIG. 2.

The first gearset 22 is arranged to transfer motive force provided bythe drive unit 18 to the wheel hub 11 and the portal shaft 26 as shownin FIGS. 1-3. The portal shaft 26 transfers motive force provided by thefirst gearset 22 to the second gearset 24, and the second gearset 24transfers motive force to the wheel hub 13. It should be understood thatthe arrangement of the drive unit 18 and drivetrain 20 can be inverted(with the drive unit 18 and first gearset 22 in the second driveassembly 16 and the second gearset 24 in the first drive assembly 14)without departing from the present disclosure.

The first gearset 22 includes a differential 30, a first output gearset32, and a first planetary gearset 34 as shown in FIG. 3. An input gear36 coupled to the drive unit 18 engages with a drive gear 38 coupled tothe differential 30 to transfer motive force delivered by the drive unit18 to the differential 30. The portal shaft 26 and a stub shaft 31 arecoupled to the differential 30 and extend in opposing directions. Thefirst output gearset 32 is coupled to the stub shaft 31, and the stubshaft 31 transfers motive force from the differential 30 to the firstoutput gearset 32 and first planetary gearset 34 for driving rotation ofthe wheel hub 11 (and attached wheel 100). In the illustrativeembodiment, the portal shaft 26, differential 30, and stub shaft 31 arearranged along rotation axis B for rotation around axis B. The firstoutput gearset 32 includes a pinion gear 33 coupled to the stub shaft 31and an output gear 35 engaged with the pinion gear 33. The output gear35 is coupled to the planetary gearset 34, and an axle shaft 37 coupledthe planetary gearset 34 engages with the wheel hub 11.

The portal shaft 26 transfers motive force from the differential 30 tothe second gearset 24 of the second drive assembly 16 for drivingrotation of the wheel hub 13 (and attached wheel 100) as shown in FIG.3. The second gearset 24 includes a second output gearset 42 coupled tothe portal shaft 26 opposite from the differential 30 and a secondplanetary gearset 44 coupled to the second output gearset 42. The secondoutput gearset 42 is similar to the first output gearset 32 and includesa pinion gear 43 coupled to the portal shaft 26 and an output gear 45engaged with the pinion gear 43. The output gear 45 is coupled to theplanetary gearset 44, and an axle shaft 47 coupled the planetary gearset44 engages with the wheel hub 13.

The differential 30 allows the portal shaft 26 and stub shaft 31 torotate at different speeds relative to one another as shown in FIGS. 3and 4. In the illustrative embodiment, the differential 30 is as an“open” differential and includes a case 50, one or more spider gears 52,54 coupled for rotation with the case 50, and side gears 56, 58 coupledthe portal shaft 26 and stub shaft 31, respectively, as shown in FIG. 4.Rotation of the case 50 moves the spider gears 52, 54 around therotation axis B, and the spider gears 52, 54 engage with the side gears56, 58 to rotate the portal shaft 26 and stub shaft 31 with rotation ofthe case 50. The spider gears 52, 54 are also rotatable relative to thecase 50 to allow relative differences in rotational speed between theportal shaft 26 and stub shaft 31 to prevent wheel drag during turningof the vehicle, for example.

Each of the planetary gearsets 34, 44 can be similarly arranged, and thefollowing description of the first planetary gearset 34 shown in FIG. 5is equally applicable to the second planetary gearset 44. The firstplanetary gearset 34 includes a sun gear 62 coupled to the output gear35, one or more planet gears 64 coupled to a carrier 66, and astationary ring gear 68 (relative to the axis A). The ring gear 68 isarranged radially outward of the planet gears 64 (relative to rotationaxis A), and the planet gears 64 are arranged radially outward of thesun gear 62. Rotation of the sun gear 62 with the output gear 35 movesthe planet gears 64 around the rotation axis A and rotates the carrier66. The axle shaft 37 is coupled to the carrier 66 for rotation with thecarrier 66. In the second planetary gearset 44 of the second gearset 24,the output gear 45 is coupled to the sun gear 62 and the axle shaft 47is coupled to the carrier 66. As contemplated by the present disclosure,in some embodiments, the differential 30 can be “locking”, “torquebiasing”, “limited slip”, or another type of differential.

Providing planetary gearsets 34, 44 in the drive assemblies 14, 16allows the use of commercial off-the-shelf (COTS) wheel hubs common tosmaller low floor vehicles, such as shuttle busses. However, it shouldbe appreciated that, in some embodiments, the first and second planetarygearsets 34, 44 can be incorporated into the wheel hubs 11, 13 with theaxle shafts 37, 47 coupled between the output gears 35, 45 and the sungears 62 of the first and second planetary gearsets 34, 44. In someembodiments, drop boxes can be used to assist in keeping the portalshaft 26 as a low as possible. Exemplary drop boxes are disclosed inU.S. Pat. No. 6,964,317, issued Nov. 15, 2005, the disclosure of whichis incorporated by reference herein in its entirety.

In some embodiments, the bridge 17 can also house additional componentssuch as, for example, electrical inverter devices providing power to thedrive unit 18, electrical and communication cables, power supplybatteries, cooling system components, and/or equipment controllers foroperating the electric axle assembly 10. Examples of other axleassemblies for low floor vehicles are shown in International PatentApplication Publication Nos. WO2019/014479, published Jan. 17, 2019, andWO2019/217861, published Nov. 14, 2019, the disclosures of which areincorporated by reference herein in their entireties.

Another embodiment of an electric axle assembly 210 in accordance withthe present disclosure is shown in FIG. 6. The electric axle assembly210 is similar to the electric axle assembly 10 of FIGS. 1-5, and likenumbers in the 200's are used to identify similar components with thedescription of the same applying equally. At least one differencebetween the electric axle assembly 210 and the electric axle assembly 10is the use of a planetary differential 230 (sometimes called a spur geardifferential) in place of the differential 30 as shown in FIGS. 6 and 7.The planetary differential 230 allows the portal shaft 226 and stubshaft 231 to rotate at different speeds relative to one another. In theillustrative embodiment, the planetary differential 230 includes a case250, one or more pairs of planet gears 252, 254 coupled for rotationwith the case 250, and side gears 256, 258 coupled the portal shaft 226and stub shaft 231, respectively, as shown in FIG. 7. Rotation of thecase 250 moves the planet gears 252, 254 around the rotation axis B, andthe planet gears 252, 254 engage with each other and with respectiveones of the side gears 256, 258 to rotate the portal shaft 226 and stubshaft 231 with rotation of the case 250. The planet gears 252, 254 arealso rotatable relative to the case 250 to allow relative differences inrotational speed between the portal shaft 226 and stub shaft 231 toprevent wheel drag during turning of the vehicle, for example.

Another embodiment of an electric axle assembly 310 in accordance withthe present disclosure is shown in FIG. 8. The electric axle assembly310 is similar to the electric axle assembly 10 of FIGS. 1-5, and likenumbers in the 300's are used to identify similar components with thedescription of the same applying equally. At least one differencebetween the electric axle assembly 310 and the electric axle assembly 10is the use of a multi-speed transmission 370 in combination with thedifferential 330 as shown in FIG. 8. In the illustrative embodiment, thetransmission 370 is a two-speed transmission and includes gears 372,374, 376, 378 and a gear selector 379. A first input gear 372 and secondinput gear 374 are coupled to the drive gear 338 for rotation with thedrive gear 338 by the drive unit 318. A first output gear 376 and secondoutput gear 378 are rotatably mounted on a support shaft 373 coupled tothe differential 330. The first input gear 372 is engaged with the firstoutput gear 376, and the second input gear 374 is engaged with thesecond output gear 378. An actuator 371 is coupled to the gear selector379 to move the gear selector 379 along the support shaft 373 relativeto the first and second output gears 376, 378.

The gear selector 379 is shown in a neutral positon between the firstand second output gears 376, 378 in FIG. 8 where the gear selector 379is disengaged from both of the first and second output gears 376, 378 toallow rotation of the first and second output gears 376, 378 aroundrotation axis B relative to the support shaft 373. The gear selector 379is rotatably fixed relative to the support shaft 373 and configured toengage with the first and second output gears 376, 378, with movement bythe actuator 371, to block rotation of the first and second output gears376, 378 relative to the support shaft 373. In a first configuration,the gear selector 379 engages with the first output gear 376 to blockrotation of the first output gear 376 relative to the support shaft 373and allow rotation of the second output gear 378 relative to the supportshaft 373. In a second configuration, the gear selector 379 engages withthe second output gear 378 to block rotation of the second output gear378 relative to the support shaft 373 and allow rotation of the firstoutput gear 376 relative to the support shaft 373. In some embodiments,the differential 230 can be used in place of the differential 330 withthe support shaft 373 being coupled to the differential 230.

The transmission 370 provides multiple, selectable gear ratios fordriving rotation of the portal shaft 326 and stub shaft 331 by the driveunit 318 as shown in FIG. 8. For example, with the gear selector 379 inthe first configuration, the first input gear 372 and first output gear376 provide a first gear ratio (e.g., a low ratio) allowing increasedtorque from the drive unit 318 to be transmitted to the portal shaft 326and stub shaft 331, at the expense of speed, allowing the vehicle toaccelerate more quickly. In a second configuration, the second inputgear 374 and second output gear 378 provide a second gear ratio (e.g., ahigh ratio) allowing increased rotational speed of the portal shaft 326and stub shaft 331, at the expense of torque, allowing the vehicle toreach a higher velocity.

In some embodiments, a size of the portal shaft 326 and bridge 317 canbe adjusted to accommodate different configurations of the low floor inthe vehicle as shown in FIGS. 8 and 9. For example, the first and seconddrive assemblies 314, 316 can be spaced apart by a width W₁ in a firstconfiguration as shown in FIG. 8. The first and second drive assemblies314, 316 can be spaced apart by a width W₂ in a first configuration asshown in FIG. 9, with the width W₂ being less that the width W₁. This isalso applicable to electric axle assemblies 10, 210 disclosed herein.

The descriptions herein of the various embodiments of electric axleassemblies may be incorporated by reference with respect to one another.

In illustrative embodiments, electric axle assemblies in accordance withthe present disclosure can be arranged for use with a vehicle such as,for example, a bus. Wheels are arranged at opposing ends of the electricaxle assemblies to support the vehicle for conveyance along a groundsurface. The electric axle assemblies propel the vehicle by transferringmotive power to the wheels in contact with the ground surface. Thevehicle can include a chassis upon which a body and other equipment maybe supported. The chassis can include frame rails; suspension componentssuch as springs, dampers, and trailing arms; and brake components suchas air cylinders, brake calipers, brake rotors, brake drums, brakehoses, and the like. The electric axle assemblies can be mountedperpendicular to the frame rails such that the vehicle travels in adirection aligned with the frame rails.

In illustrative embodiments, the electric axle assemblies may beconfigured for “single-wheel” applications and “dual-wheel”applications. In “single-wheel” applications a single wheel is coupledto each end of the electric axle assembly. Likewise, in “dual-wheel”applications, wheels are arranged in pairs at each end of the electricaxle assembly. Vehicles requiring increased payload or towing capacityare one example of a “dual-wheel” application. Vehicles that require afurther increased payload/towing capacity may be equipped with two ormore electric axle assemblies. Some vehicles may require drive devicesother than wheels. For example, crawler tracks or rail wheels may becoupled to the electric axle assembly to propel the vehicle. Theelectric axle assembly may be mounted to the vehicle in the front and inthe rear to realize various drive types such as front-wheel drive,rear-wheel drive, and all/four-wheel drive.

In illustrative embodiments, vehicle performance is optimized when thewheels are in constant contact with the ground. In order to more easilyfollow the ground, a suspension system can movably couple the electricaxle assembly to the frame rails. The suspension system allows theelectric axle assembly to move relative to the frame rails and urges thewheels toward the ground when the vehicle encounters imperfections inthe ground. The suspension system may include springs and dampers, whichabsorb movement and improve ride quality; control arms that constrainthe movement of the electric axle assembly; and other elements asdetermined by the application such as steering and kinematic linkages.The electric axle assembly may also be mounted to a vehicle that was notoriginally equipped with an electric axle assembly. The electric axleassembly can be retrofit to these vehicles to offer an electricdriveline upgrade.

In illustrative embodiments, the electric axle assembly may be utilizedin both hybrid-electric and fully-electric vehicles. In a fully-electricvehicle, electricity to power the electric axle assembly may be storedin a battery mounted to the chassis. Alternatively, electricity may besupplied from an external power source, such as an overhead wire orthird rail system. If the vehicle is configured as a hybrid-electricvehicle, an internal combustion engine may be mounted to the chassis andcoupled to a drive unit capable of generating electricity; theelectricity may power the electric axle assembly directly, or may bestored in a battery.

In illustrative embodiments, the electric axle assembly can include adrive housing (sometimes called a case) that houses at least one driveunit and drives a gear train (sometimes called a drive train). The driveunit is coupled to the drive housing and engaged with the gear train totransfer power to the wheels. The gear train may include a series ofgears and shafts supported for rotation on the electric axle assembly.Typically, bearings are used to reduce friction between rotatingcomponents of the gear train. Various bearing types may be useddepending on the requirements of the application, for example, journal(plain) bearings, roller bearings, ball bearings, etc. Friction isfurther reduced through the use of a lubricant, such as oil supplied tocontact surfaces between components, such as gear teeth and bearings, toprevent wear and to reduce heat. The electric axle assembly may furtherinclude two wheel ends (sometimes called wheel hubs). It should beappreciated that the drive housing and wheel ends may be constructed andcoupled in a variety of ways. The electric axle assembly can beconfigured for use in a low-floor bus and include multiple drivehousings, each arranged on opposing sides of the electric axle assembly.The drive housings may be assembled using fasteners and the like.

In the illustrative embodiments, the electric axle assembly includes adrive unit, such as an electric motor, combined with a single speed or atwo speed transmission configuration to give both launch performance andvelocity performance. In addition, the electric axle assembly includesan axle housing that integrates the electric motor and transmissioncompactly, supplies cooling for heat dissipation, and transmits vehicleloads to suspension components. The electric axle assembly may also bemounted to a vehicle that was not originally equipped with an electricaxle assembly, and can be retrofit to these vehicles to offer anelectric driveline upgrade. For example, a low floor bus originallyequipped with a traditional axle assembly may utilize the electric axleassembly in place of the traditional axle assembly.

In illustrative embodiments, the electric axle assembly includes adrivetrain (sometimes called a reduction assembly) that is driven by asingle drive unit, and an axle housing that encloses the reductionassembly and the single drive unit. The single drive unit drives thewheels (sometimes called wheel assemblies) that are coupled to theelectric axle assembly. The reduction assembly includes a first gearset, a second gear set, and portal axle shaft coupled between the firstgear set and the second gear set. The first gear set is coupled to afirst axle shaft that is orientated along a first axis of rotation. Thesecond gear set is coupled to a second axle shaft that is orientatedalong a second axis of rotation with said first and second axle shaftsextending in opposite directions. The first axle shaft is coupled to afirst wheel end (sometimes called a wheel hub) and the second axle shaftis coupled to a second wheel end. The first and second wheel ends can beof any design or configuration, such as COTS wheel ends, and are coupledto corresponding vehicle wheel assemblies. The first axle shaft isorientated coaxial with the second axle shaft such that the first andsecond axle shafts are orientated along the same axis of rotation. Insome embodiments, the first axle shaft may be offset from the secondaxle shaft such that the first axis of rotation is offset a radialdistance from the second axle shaft.

In illustrative embodiments, the axle housing includes a first outerunit (sometimes called a drive assembly), a second outer unit, and abridge. The first and second outer units are generally illustrated ashaving somewhat rectangular configurations, but can be of any suitabledesign or configuration in order to house the associated componentsdiscussed herein. The first and second outer units can also havedifferent configurations from one another.

In illustrative embodiments, the first outer unit encloses the singledrive unit and the first gear set with the first axle shaft and theportal axle shaft partially disposed within the first outer unit. Thesecond outer unit encloses the second gear set with the second axleshaft and the portal axle shaft partially disposed within the secondouter unit. The bridge is coupled between the first outer unit and thesecond outer unit and encloses a portion of the portal axle shaftextending between the first gear set and the second gear set. In someembodiments, the bridge may also house additional components such as,for example, electrical inverter devices providing power to the driveunit, electrical and communication cables, power supply batteries,and/or equipment controllers for operating the electric axle assembly.The outer units may be arranged at opposite ends of the bridge, and maybe spaced laterally from each other relative to the vehicle. Mounts canbe used to attach the electric axle assembly to the vehicle and/orsuspension arms that may be coupled to the mounts to movably attach theelectric axle assembly to the vehicle.

In illustrative embodiments, the portal axle shaft extends along a thirdaxis of rotation that is offset a distance from the first and secondaxle shafts along a vertical axis. The portal axle shaft extends throughor about the bridge of the axle housing between the opposing outerunits. Each outer unit has a width, which can be decreased in order toincrease the width of the low floor of the vehicle. The bridge may beintegrally formed with the outer units or may be coupled to the outerunits, such as with fasteners. For example, the bridge may be welded,pressed, or bolted to the outer units.

In illustrative embodiments, the first gear set includes an input gear,a differential gear set, a first output gear set, and a first planetarygear set. The input gear is driven by the single drive unit. Thedifferential gear set is coupled to and driven by the input gear totransfer rotational torque from the single drive unit to the portal axleshaft and to the first output gear set, thereby eliminating the need fora planetary gear set at the wheel end. For example, in some embodiments,the input gear may be coupled to a ring gear of the differential gearset. The first output gear set includes an output shaft that is coupledto and driven by the differential gear set. The output shaft includes apinion that is coupled to an output gear that drives the first planetarygear set. In one embodiment, the first planetary gear set may include aplanetary gear shaft that is coupled to the output gear at one end ofthe planetary gear shaft, and a sun gear that is coupled to the otherend of the planetary gear shaft. In the illustrated embodiment, thefirst axle shaft is coupled to the first planetary gear set and to thefirst wheel assembly for transferring rotational torque from the singledrive unit to the first wheel assembly via the differential gear set,the first output gear set, and the first planetary gear set.

In illustrative embodiments, the differential gear set may include aplanetary differential, with the portal axle shaft and the output shaftcoupled to the planetary differential. In other embodiments, thereduction assembly may include portal axle shafts having different shaftlengths to accommodate a width of the bridge, which can be decreased inorder to increase the width of the low floor of the vehicle.

In illustrative embodiments, the second gear set includes a secondoutput gear set and a second planetary gear set. The second output gearset is coupled to the portal axle shaft and to the second planetary gearset for transferring rotational torque from the portal axle shaft to thesecond planetary gear set, thereby eliminating the need for a planetarygear set at the wheel end. For example, in one embodiment, the secondoutput gear set may include a second output gear that is coupled to apinion of the portal axle shaft. The second planetary gear set mayinclude a second planetary gear shaft that is coupled to the secondoutput gear at one end of the second planetary gear shaft, and a secondsun gear that is coupled to the other end of the second planetary gearshaft. The second axle shaft is coupled to the second planetary gear setand the second wheel assembly for transferring rotational torque fromthe single drive unit to the second wheel assembly via the differentialgear set, the portal axle shaft, the second output gear set, and thesecond planetary gear set.

In illustrative embodiments, the reduction assembly may include one ormore drop boxes. For example, the reduction assembly may include a dropbox coupled between the portal axle shaft and the second planetary gearset. One or more drop boxes may have a single drop, which can be a gearreduction or can be a 1:1 drop. In some embodiments, the reductionassembly does not incorporate a gear reduction across the portal axleshaft. In another embodiment, the reduction assembly may include one ormore drop boxes having different drops, with a first drop box having asingle gear drop and a second drop box having a double gear drop. Thedrop boxes may have the same or a different gear reductions.

In illustrative embodiments, the reduction assembly includes a two speedtransmission configuration to give both launch performance and velocityperformance. For example, the first gear set may include a speed changemechanism that is coupled between the input gear and the differentialgear set and is selectively shiftable between a first ratio and a secondratio to change the rotational torque transferred to the first andsecond axle shafts. The speed change mechanism includes a reduction gearset that is driven by the input gear and an output gear set that isdriven by the reduction gear set. The reduction gear set includes aninput reduction gear that is coupled to the input gear, a firstreduction gear and a second reduction gear. The output gear set iscoupled to the differential gear set and includes and output shaft, afirst output gear, and a second output gear. The output shaft is coupledto the differential gear set for transferring rotational torque from thereduction gear set to the differential gear set. The two output gearsare each rotatably supported on the output shaft. The first output gearis coupled to the first reduction gear and corresponds to the firstratio of the reduction assembly, and the second output gear is coupledto the second reduction gear and corresponds to the second ratio of thereduction assembly. In the illustrated embodiment, each of the outputgears can spin freely on the output shaft such that when thecorresponding ratio is not engaged, no torque is transferred between theoutput shaft and the output gears. In one embodiment, the output shaftis orientated coaxially with the portal axle shaft and may include aninner surface that defines a bore that is sized and shaped to receivethe portal axle shaft therethrough.

In illustrative embodiments, a shift mechanism (sometimes called a gearselector) is positioned between the first output gear and the secondoutput gear and is configured to selectively engage the first outputgear and the second output gear. Each output gear may include a splinedportion engageable with the shift mechanism to rotatably couple theoutput gears to the output shaft. The shift mechanism may include ashift sleeve, a shift fork, and an actuator. The shift sleeve is coupledto the output shaft such that the shift sleeve and the output shaftrotate at the same speed. The shift fork is operably coupled to theactuator and to the shift sleeve such that movement of the actuatorcauses the shift fork to slide the shift sleeve along the output shaft.The shift sleeve is selectively engageable with the first output gearand the second output gear to place the reduction assembly in either thefirst ratio or the second ratio, respectively. The shift sleeve and theoutput gears include mating engagement features that, when engaged,rotatably couple the output gears to the output shaft. The engagementfeatures may include splines, a dog clutch, or a synchronizer to aidshifting. Additionally, the shift fork and shift sleeve may be movableinto a neutral position where neither of the output gears are engagedwith the shift sleeve. The actuator may be controlled manually orautomatically. The actuator may be responsive to hydraulic pressure,pneumatic pressure, or electronic signals generated by a control module.Alternatively, the actuator may include a mechanical linkage controlledby an operator.

While the disclosure has been illustrated and described in detail in thedrawings and foregoing description, such an illustration and descriptionis to be considered as exemplary and not restrictive in character, itbeing understood that only illustrative embodiments have been shown anddescribed and that all changes and modifications that come within thespirit of the disclosure are desired to be protected.

1. An electric axle assembly comprising: a suspension frame; a firstdrive assembly and a second drive assembly coupled to opposing sides ofthe suspension frame; a first wheel hub coupled to the first driveassembly and a second wheel hub coupled to the second drive assembly,the first and second wheel hubs arranged to support wheels for rotationabout a first axis; a drive unit arranged in the first drive assembly;and a drivetrain comprising: a first gearset arranged in the first driveassembly, the first gearset including a differential arranged along thesecond axis, a stub shaft coupled to the differential, a first outputgearset coupled to the stub shaft, and a first planetary gearset coupledto the first output gearset and the first wheel hub; a second gearsetarranged in the second drive assembly, the second gearset including asecond output gearset and a second planetary gearset coupled to thesecond output gearset and the second wheel hub; and a portal shaftextending between the first and second gearsets, the portal shaftcoupled to the differential and arranged for rotation about a secondaxis offset from the first axis; wherein the second output gearset iscoupled to the portal shaft opposite of the differential, the drive unitis configured to provide motive force to the differential, and theportal shaft is configured to transfer motive force from thedifferential to the second output gearset.
 2. The electric axle assemblyof claim 1, wherein a bridge of the suspension frame is offset from thefirst axis, and wherein the portal shaft is arranged to substantiallyalign with the bridge.
 3. The electric axle assembly of claim 1, whereinthe differential includes a case, a spider gear coupled to the case forrotation with the case about the second axis, and side gears coupled tothe portal shaft and stub shaft, respectively, and engaged with thespider gear.
 4. The electric axle assembly of claim 1, wherein thedifferential includes a case, a pair of planet gears coupled to the casefor rotation with the case about the second axis, and side gears coupledto the portal shaft and stub shaft, respectively, and wherein the planetgears are engaged with each other and with respective ones of the sidegears.
 5. The electric axle assembly of claim 1, wherein the firstoutput gearset includes a pinion gear coupled to the stub shaft and anoutput gear coupled to the first planetary gearset and engaged with thepinion gear.
 6. The electric axle assembly of claim 5, wherein theoutput gear is arranged for rotation about the first axis.
 7. Theelectric axle assembly of claim 5, wherein the first planetary gearsetincludes a sun gear coupled to the output gear for rotation about thefirst axis, a planet gear arranged radially outward of the sun gear andengaged with the sun gear, a ring gear arranged radially outward of theplanet gear and engaged with the planet gear, and a carrier coupled tothe planet gear and the first wheel hub, and wherein the ring gear isstationary relative to the first axis.
 8. The electric axle assembly ofclaim 1, wherein the second output gearset includes a pinion gearcoupled to the portal shaft and an output gear coupled to the secondplanetary gearset and engaged with the pinion gear.
 9. The electric axleassembly of claim 8, wherein the output gear is arranged for rotationabout the first axis.
 10. The electric axle assembly of claim 8, whereinthe second planetary gearset includes a sun gear coupled to the outputgear for rotation about the first axis, a planet gear arranged radiallyoutward of the sun gear and engaged with the sun gear, a ring geararranged radially outward of the planet gear and engaged with the planetgear, and a carrier coupled to the planet gear and the second wheel hub,and wherein the ring gear is stationary relative to the first axis. 11.The electric axle assembly of claim 1, further comprising a drive gearcoupled to the differential and arranged to receive motive force fromthe drive unit.
 12. The electric axle assembly of claim 1, furthercomprising a transmission comprising: a first input gear and secondinput gear coupled to a drive gear, the drive gear arranged to receivemotive force from the drive unit; a first output gear and a secondoutput gear rotatably mounted on a support shaft coupled to thedifferential, the first input gear engaged with the first output gearand the second input gear engaged with the second output gear; and agear selector mounted on the support shaft, the gear selector movablealong the support shaft and rotatably fixed relative to the supportshaft, wherein the gear selector is configured to selectively engagewith the first or second output gear to block rotation of the engagedfirst or second output gear relative to the support shaft.
 13. Theelectric axle assembly of claim 12, wherein: in a first configuration,the gear selector engages with the first output gear to block rotationof the first output gear relative to the support shaft and allowrotation of the second output gear relative to the support shaft toprovide a low ratio of the transmission; and in a second configuration,the gear selector engages with the second output gear to block rotationof the second output gear relative to the support shaft and allowrotation of the first output gear relative to the support shaft toprovide a high ratio of the transmission.
 14. The electric axle assemblyof claim 13, further comprising an actuator configured to move the gearselector to the first and second configurations.
 15. An electric axleassembly comprising: a suspension frame; a first drive assembly and asecond drive assembly coupled to opposing sides of the suspension frame;a first wheel hub coupled to the first drive assembly and a second wheelhub coupled to the second drive assembly, the first and second wheelhubs arranged to support wheels for rotation about a first axis; a driveunit arranged in the first drive assembly; and a drivetrain comprising:a first gearset arranged in the first drive assembly and coupled to thefirst wheel hub; a second gearset arranged in the second drive assemblyand coupled to the second wheel hub; and a portal shaft arranged forrotation about a second axis offset from the first axis, the portalshaft extending between the first and second gearsets; wherein the driveunit is configured to provide motive force to a differential of thefirst gearset, the portal shaft is coupled to the differential, and thedifferential is configured to transfer motive force to the first wheelhub through the first gearset and to the second wheel hub through theportal shaft and second gearset.
 16. The electric axle assembly of claim15, wherein a bridge of the suspension frame is offset from the firstaxis, and wherein the portal shaft is arranged to substantially alignthe bridge.
 17. The electric axle assembly of claim 15, wherein thedifferential is arranged along the second axis for rotation about thesecond axis.
 18. The electric axle assembly of claim 15, furthercomprising a drive gear coupled to the differential and arranged toreceive motive force from the drive unit.
 19. The electric axle assemblyof claim 15, further comprising a transmission comprising: a first inputgear and second input gear coupled to a drive gear, the drive geararranged to receive motive force from the drive unit; a first outputgear and a second output gear rotatably mounted on a support shaftcoupled to the differential, the first input gear engaged with the firstoutput gear and the second input gear engaged with the second outputgear; and a gear selector mounted on the support shaft, the gearselector movable along the support shaft and rotatably fixed relative tothe support shaft, wherein the gear selector is configured toselectively engage with the first or second output gear to blockrotation of the engaged first or second output gear relative to thesupport shaft.
 20. The electric axle assembly of claim 19, wherein: in afirst configuration, the gear selector engages with the first outputgear to block rotation of the first output gear relative to the supportshaft and allow rotation of the second output gear relative to thesupport shaft to provide a low ratio of the transmission; and in asecond configuration, the gear selector engages with the second outputgear to block rotation of the second output gear relative to the supportshaft and allow rotation of the first output gear relative to thesupport shaft to provide a high ratio of the transmission.
 21. Theelectric axle assembly of claim 20, further comprising an actuatorconfigured to move the gear selector to the first and secondconfigurations.